Front wheel energy recovery system

ABSTRACT

A kinetic energy recovery system (“KERS system”) and motorcycle equipped with the same is disclosed. The KERS system may be mechanical, hydraulic, or a combination thereof. In an embodiment, motorcycle includes a rear wheel, an electric motor, a motor shaft, and a front wheel equipped with a wheel hub that includes a sprag clutch. The motor shaft can be fitted with a motor drive sprocket that drives a jackshaft chain that in turn drives a jackshaft input sprocket that is fitted to the jackshaft. Jackshaft input sprocket may be installed in conjunction with a sprag clutch that allows the rear wheel to free wheel during coasting while the front wheel KERS system is engaged. The motor harvests kinetic energy from the front wheel without simultaneously powering the rear wheel while the use of a geared dead zone allows the front and rear wheels to not lock together to improve safety.

This application is a continuation of U.S. patent application Ser. No.12/897,534, filed Oct. 4, 2010, which is incorporated by reference forall purposes in its entity as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a system and method for energy recoveryusing the front wheel of a vehicle.

2. Discussion of the Related Art

Electric and hybrid powered vehicles offer a means of transportationthat emit substantially no pollutants and produce little noise. Thesefeatures are especially important at a time when such pollution hasbecome a major concern. Although major advances have been made inelectric and hybrid powered automobiles, the same cannot be said fortwo-wheeled and three-wheeled vehicles such as motorcycles, scooters,mopeds, and trikes, hereinafter referred to as “motorcycle(s)”.

Motorcycles have a wide variety of uses and the potential to positivelyimpact society and the environment through reduction of congestion andpollution in addition to other benefits arising from their propagation.Gasoline burning versions of these vehicles are used for recreationalpurposes, as a main means for transportation in every day use, and evenin competitive racing. One major concern with using electric motors invehicle design is battery life and battery size, which impact vehiclepower and range, especially on motorcycles where space to accommodatebatteries is extremely limited.

Electric and hybrid powered vehicles rely on electricity from anon-board electricity storage source such as a battery, capacitor, orcombination of both (hereinafter “electrical accumulator”). The mostcommon electrical accumulator in use today is a battery, which must berecharged periodically, either during or after use. The most commonmeans for recharging an electric vehicle's battery is by plugging itinto an AC power outlet for a long period of time. For hybrid vehicles,charging may occur during use from power delivered by an on-boardinternal combustion engine. Battery size becomes a key issue asconsumers are demanding that electric vehicles operate at extendedranges that require larger and thus heavier batteries that are morecostly and are not conducive to small vehicles such as motorcycles.

For these and other reasons, historically motorcycles have involved theuse of only gasoline powered internal combustion engines. These vehicleshave generally been gasoline powered because they can be quicklyrefilled from ubiquitous filling stations, can generate substantialpower for their weight, and are relatively inexpensive. Today's batterytechnology does not provide for long duration sufficient to make anelectric two or three-wheeled vehicle competitive with its gasolinepowered counterparts, and so manufacturers have been slow to produceelectric motorcycles. These drawbacks, however, can be rectified by asystem that is capable of producing substantial regeneration of thebattery during use, such as during regenerative braking events, in orderto recharge the battery and extend vehicle range for greater performanceand consumer acceptance.

One approach to providing regeneration of a battery during use is by theuse of a kinetic energy recovery system (“KERS system”), which is alsoknown as a regenerative braking system or energy recovery system.Kinetic energy recovery has been developed for electrically poweredfour-wheel production and race vehicles, but the systems developed forfour-wheel vehicles (hereinafter “cars”) are not able to be effectivelyutilized in motorcycles due to issues relating to size, weight, vehiclestability, and for additional and non-obvious reasons.

One way to construct a KERS system that is known in the art is toutilize a “wheel motor”, which is an electric motor installed inside thestructure of one or more of a vehicle's wheels. A wheel motor providesregenerative braking torque that can be used to charge an on-boardbattery. One fundamental problem of wheel motors is they must be of alarge enough capacity to harvest a meaningful amount of energysufficient to justify their weight and cost. In one example analysisperformed by the inventors, a racing motorcycle was instrumented with adata acquisition system and it was discovered that during heavy braking,an amount of energy equivalent to 150 horsepower was being converted toheat by the traditional friction braking system installed on the frontwheel. To capture this energy for use in battery charging would requirea 150 horsepower wheel motor to be installed inside the front wheel,which would weigh more than 100 lbs and be extremely expensive.Additionally, the effect of adding more than 100 lbs to the front wheelof a motorcycle would create an extremely unstable and dangerous vehicledynamics situation, since steering, balance, wheel size, and unsprungweight are all degraded considerably, assuming the bulky 150 horsepowermotor could even be packaged inside a front wheel in the first place.Accordingly, there is a need for a system with the lightest possiblecomponents located at the front wheel that can transmit significantenergy away from the front wheel to be converted to electricity by agenerating device located separately from the front wheel, such asinside the frame of the motorcycle.

The negative effects that wheel motors present to motorcycles can bepartially mitigated in electric or hybrid cars. Typically, cars steer byusing the two front wheels, giving more steering stability than theone-wheel steering found on motorcycles. Cars do not have to lean duringcornering and being larger, weight is not as much of a concern for carsas it is for motorcycles, which rely on being nimble for safe handlingespecially during cornering on windy roads. During braking, cars spreadthe traction and heat rejection work over four wheels, and the rearwheels of a car typically handle more braking effort than does the rearwheel of a motorcycle. In one example, the braking proportion of a carmay be 70% front wheels and 30% rear wheels. For a motorcycle, thebraking loads may be more like 90% front and 10% rear, and it is notuncommon for the rear wheel to actually lift off of the pavement duringheavy braking, which means the front wheel is handling 100% of thebraking.

Cars may be designed with electric motors driving some or all of thewheels; either by the use of wheel motors inside the actual wheels, orby the mechanical coupling of a motor to a driven wheel. Whenever amotor is coupled to drive a particular wheel, it is convenient to usethat same motor for regeneration simply by configuring the motorcontroller for that motor to initiate regenerative braking torque ratherthan forward propulsion torque with little or no additional structurerequired. A very large percentage of electric and hybrid cars availabletoday use a front wheel drive powertrain, which greatly facilitates theuse of regenerative braking in such vehicles. Yet despite the steadyincrease of manufacturer interest in electric cars and the ease withwhich they may deploy a KERS system on their front wheel drive designs,electric motorcycles are extremely rare, and almost none of those thathave been built use any kind of regenerative braking systems. This isbecause conventional wisdom in the field of electric motorcycles holdsthat since the electric motor is mechanically coupled to drive the rearwheel (where there is little regenerative benefit under braking due tothe light loading of the rear wheel as previously discussed) suchsystems are ineffective on a motorcycle. Research and analysis conductedby the inventors on the effectiveness of rear wheel KERS systemsindicate that such a configuration can be expected to produce no morethan 1 C of charge current in the best case scenario, whereasembodiments in accordance with the present invention can deliver morethan 10 times that amount through the collection of energy from thefront, non-driven wheel. To the knowledge of the inventors of thisapplication, no one in the art of electric motorcycle design has evenrecognized and certainly not addressed the problem of how to recover theabundant energy available from the front wheel of a motorcycle underbraking, which is otherwise wasted as heat. Another factor that hascaused the electric motorcycle industry to ignore KERS systems is thevery high crash danger arising from the use of rear wheel regenerationbecause applying any braking torque to a lightly loaded rear wheel,especially when leaning into a turn, easily locks up the wheel andcauses rapid loss of traction and control.

Other KERS system constructions may be used such as via hydraulicaccumulators or flywheel storage, but like wheel motors, each havedrawbacks that render them inappropriate for motorcycle applications.Companies such as Eaton Corporation have successfully implemented KERSsystems known by their trademark as Hydraulic Launch Assist (“HLA®”) forheavy commercial vehicles such as garbage trucks. During braking, ahydraulic pump/motor coupled to the drivetrain creates hydraulicpressure inside a large hydraulic accumulator that acts to compress agas such as nitrogen. This stored pressure is later released as a fairlyshort burst during acceleration back to the hydraulic pump/motor and isknown to improve the efficiency of such vehicles. The use of a highpressure accumulator sufficient to provide a meaningful KERS systembenefit on a motorcycle, coupled with the inefficiencies inherent inthis type of accumulator system make it impractical for a motorcycle.Similarly, the storage of braking energy in a flywheel has beensuccessfully implemented by Porsche AG in their 911 GT3 R Hybridracecar. Using a 40,000 RPM flywheel provided by Williams F1 and two 80horsepower electric motors, Porsche has reported their KERS systemequipped racecar delivering an average of 6.2 mpg during race conditionsversus 5.6 mpg for their non-KERS system equipped racecar at theNurburgring race track in April, 2010. While this is a noteworthyimprovement in fuel economy, the packaging and handling impact on amotorcycle with a 40,000 RPM flywheel mounted to it combined with theextreme cost, cooling requirements, and limited energy storage makeflywheels impractical for motorcycles.

The use of a mechanical or hydraulic (non-accumulator hydraulic system)energy transfer system holds promise as the basis of an effective KERSsystem solution for a motorcycle so long as certain precautions aretaken with respect to safety and vehicle dynamics. The application ofgears, shafts, pumps and other such structures to the front wheel andsuspension of a motorcycle presents a number of challenges as it is easyto upset the safe handling characteristics of a two or three-wheeledvehicle, which are more sensitive to such changes than are cars. Evenwith the safe design and installation of a mechanical or hydraulic KERSsystem, safety and vehicle dynamics are dependent on the carefulactuation and precise control of the system during operation asdisclosed in more detail herein below.

One recent development in the area of using mechanical gears and shaftson a dirt bike or bicycle are described in U.S. Pat. No. 6,505,699, andrelated U.S. Patent Application Publication No. 2009/0188738 and U.S.Pat. Nos. 6,439,592; 6,182,991; 6,161,854; 7,487,854; 7,328,766; and6,161,855 issued to Steven J. Christini, et al. all of which areincorporated by reference herein. The system described in U.S. Pat. No.6,505,699 is designed to transfer a limited percentage of availablepower from a standard gasoline burning internal combustion engine to thefront wheel of a dirt bike at certain times during operation. In doingso, Christini has achieved a dirtbike that may be operated in eitherstandard rear-wheel drive or in a two-wheel drive mode, as manuallydetermined from a rider-operated lever, depending on available tractionin the dirt. U.S. Pat. No. 6,505,699 does not disclose or provide anyteaching on recovering energy from the front wheel for use in rechargingbatteries or for any other purpose, and actually precludes such energytransfer by the teaching of one-way freewheel sprag clutches in thefront wheel that operate to allow the motor to drive the front wheel butdo not allow the front wheel to back drive the motor for regeneration.Additionally, U.S. Pat. No. 6,505,699 does not even discloseimplementation in an electric powered vehicle.

It is clear that manufacturers and inventors of electric motorcycleshave failed to recognize and address the problem of recovering kineticenergy from the front wheel. Limited efforts have been made to implementrear wheel KERS systems, but the poor regeneration provided by thelightly loaded rear tire have led most to abandon the pursuit ofon-board recharging altogether. Industry experts have been quoted assaying that KERS systems on a motorcycle are a waste of time. KTM PowerSports AG is one company to try rear wheel KERS system on a motorcycle.KTM is a well known manufacturer of motorcycles and also endeavors torace their motorcycles in various events around the world. KTM hassubstantial engineering and financial resources. KTM reported using arear wheel KERS system in the 2008 Valencia Grand Prix race on a 125 cctwo-stroke motorcycle that generated an additional 2.68 horsepower andwas subsequently banned by race organizers.

Unfortunately, the limited battery capacities available in the currentstate of the art combined with the industry's failure to recognize oremploy the front wheel as a source of significant recharging energy, hascombined to relegate the fledgling electric motorcycle industry tonovelty status with an uncertain future due to limited vehicle range andperformance.

Accordingly, there is an urgent need for a regenerative braking systemthat can capture significant energy from the front wheel of amotorcycle, that is also lightweight, efficient in its energy transfer,easy to package, cost effective, and does not impede the maneuverabilityor safety of the KERS system equipped motorcycle.

SUMMARY OF THE INVENTION

One embodiment of a front wheel kinetic recovery system for a motorcyclemade in accordance with the claimed invention substantially obviates thelimitations and disadvantages of the related art.

An advantage of an embodiment of the claimed front wheel KERS system fora motorcycle may be to provide a mechanical system with counterbalancedtorque reactions and moments of inertia for the portion of the KERSsystem that is co-located with the front wheel and suspension so as toavoid creating a torque steering effect. This in turn improves thevehicle dynamics and safety for the rider.

Another advantage of an embodiment of the claimed front wheel KERSsystem for a motorcycle may be the ability to easily install a hydraulicversion of the claimed invention to a new or existing motorcycle withminimal modifications.

Another advantage of an embodiment of the claimed front wheel KERSsystem for a motorcycle may be the ability to transmit substantialenergy from the front wheel to an electricity generating device locatedseparately from the front wheel without interfering with steering rangeof motion or the telescoping action of the front suspension.

Another advantage of an embodiment of the claimed front wheel KERSsystem for a motorcycle may be the ability to transfer substantialenergy from the front wheel to extend the life of the on-boardelectrical accumulator charge and thus allow for the use of morepowerful motors with smaller battery packs that would otherwise bequickly discharged.

Another advantage of an embodiment of the claimed front wheel KERSsystem for a motorcycle may be the ability to transfer substantialenergy from the front wheel to extend the life of the electricalaccumulator charge and thus allow for a motorcycle with a fixed capacitymotor and electrical accumulator to travel over an extended rangerelative to a non-KERS system equipped motorcycle of the same capacitymotor and electrical accumulator.

Another advantage of an embodiment of the claimed front wheel KERSsystem for a motorcycle may be to provide a system that allows forcomprehensive control over the KERS system both by manual and/orautomatic controls.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention may be realized andattained by the exemplary structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof exemplary embodiments, as embodied and broadly described; a vehiclepowered at least partially by at least one electric motor comprising anelectrical accumulator to store and provide electricity to the at leastone electric motor; a front wheel and at least one rear wheel; ahandlebar; a front wheel kinetic energy recovery system operating totransmit energy from said front wheel to an electricity generatingdevice located separately from said front wheel; whereby electricity maybe transmitted from said electricity generating device to saidelectrical accumulator during vehicle operation.

In another aspect of exemplary embodiments a method of regeneratingenergy in an electrical accumulator comprising: operatively connecting akinetic energy recovery system to a front wheel of a two-wheel orthree-wheel vehicle; transferring energy collected from the front wheelto an electric motor by applying a load on a motor shaft; controllingthe motor to generate electricity using the load applied on the motorshaft.

In another aspect of exemplary embodiments, a method of determining thesuitability of an electrical accumulator for use with a front wheelkinetic energy recovery system comprising: calculating an amount of KERSsystem charge current obtainable from the front wheel kinetic energyrecovery system; calculating a current level and duration for a desiredduty cycle for an electrical accumulator for at least one dischargeevent and one energy recovery event; and testing the electricalaccumulator using the calculated current level and duration from eachevent.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1A is a left side view of an electric motorcycle equipped with afront wheel KERS system in accordance with one exemplary embodiment.

FIG. 1B is a top down view of an electric motorcycle equipped with afront wheel KERS system in accordance with one exemplary embodiment.

FIG. 2 is front view of a mechanical KERS system equipped motorcycleshowing the steering head, triple clamps, front suspension (forks),steering apparatus and sectioned front wheel hub.

FIG. 3 is a more detailed exploded view of the front wheel hub.

FIG. 4 is a representation of a series of bevel gears and shafts locatedin the steering head portion of the motorcycle frame.

FIG. 5 is a representation of the left side view of a KERS systemequipped motorcycle including the steering head portion of themotorcycle frame, shafts and universal joints, upper gearbox, chains,motor shaft, jackshaft, and electric motor mounting plates.

FIG. 6A illustrate front and rear views of a KERS system equippedmotorcycle, including the steering head portion of the motorcycle frame,shafts and universal joints, upper gearbox, chains, motor shaft,jackshaft, and electric motor mounting plates.

FIG. 6B is an elevated view of a KERS system equipped motorcycle,including the steering head portion of the motorcycle frame, shafts anduniversal joints, upper gearbox, chains, motor shaft, jackshaft, andelectric motor mounting plates.

FIG. 6C is a cross-sectional view of the jackshaft where the rear wheelsprag clutch is located.

FIG. 7 is a top down view of the layout of a KERS system equippedelectric motorcycle including the electric motor, motor shaft,jackshaft, chains, and drive sprockets.

FIGS. 8A-8B are graphical representations of the “dead zone” created bythe use of front and rear wheel one-way sprag clutches combined with thecareful gearing of the front and rear wheels in accordance withexemplary embodiments.

FIG. 9 is a view of a KERS system control device in the form of arider-operated KERS brake lever and position sensor.

FIG. 10A is a block diagram showing the major components and signal flowon a KERS system equipped motorcycle in accordance with an exemplaryembodiment.

FIGS. 10B-10C are block diagrams showing the two basic modes ofoperation of a KERS system equipped motorcycle in accordance with anexemplary embodiment; current flowing from the electrical accumulator tothe motor to propel the vehicle, and current flowing from the motor backto the electrical accumulator for recharging during braking.

FIG. 11 is a graph showing a direct correspondence between a rideroperated KERS brake lever/position sensor and a regenerative torquecommand; also shown is an alternative soft onset feature to avoidsending abrupt braking torque to the front wheel via the KERS brakelever.

FIG. 12A is series of two plots showing the kinetic energy recoverycharge and discharge current profile over the course of onerepresentative lap of a representative racetrack.

FIG. 12B is a plot resulting from a race simulation test performed on acandidate electrical accumulator, in this case a lithium-ion polymerbattery cell.

FIG. 13 is a graph showing the reduced weight and capacity of anelectrical accumulator such as a battery pack when a KERS system is usedwith a motor of a certain horsepower level.

FIG. 14 is a graph showing the effect of a KERS system on maintaining ahigher electrical accumulator charge level during use (such as during arace); during braking, the KERS system equipped motorcycle experiencesrises in voltage, while the same motorcycle without a KERS system seesflat voltage during braking and is quickly depleted prior to the end ofthe race.

FIG. 15 is a graph showing the effect that different amounts of KERSsystem force taken from the front wheel along with the KERS systemregeneration charge limit has on the amount of electrical accumulatorcapacity required for a particular journey (in this case, one lap of anexemplary race track).

FIGS. 16A-16B are a series of graphs showing how much power reduction isrequired for a non KERS system equipped motorcycle to complete aparticular journey (in this case, one lap of an exemplary race track)that a KERS system equipped motorcycle could complete using full power.

FIG. 17A is a side view of an electric motorcycle equipped with a frontwheel hydraulic KERS system in accordance with an exemplary embodiment;a hydraulic pump is located on the front wheel, a hydraulic pump/motoris located on the electric motor shaft, and hydraulic lines, reservoir,and fluid is shown; also shown is a switching valve with two states, Aand B.

FIGS. 17B-17C is a series of diagrams of a gerotor style hydraulic pump,hydraulic motor, electric motor, drive sprocket.

FIG. 17D is a block diagram exemplifying the operation of an hydraulicKERS system.

FIG. 18 is a section view diagram of a dual clutch pack differentialsplined to the output/input shaft of an electric motor used to vary thetransfer of energy between the electric motor, and the front and rearwheels by the use of clutch packs and pressure plates.

FIG. 19 is a view of an alternate front suspension arrangement to thecommonly used front forks; exemplary embodiments may include any type offront suspension for a motorcycle.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Reference will now be made in detail to various embodiments, examples ofwhich are illustrated in the accompanying drawings.

Embodiments relate to a kinetic energy recovery system and a motorcycleequipped with the same. It should be noted that for simplicity, thefollowing paragraphs discuss embodiments relating to a motorcycle. Thisshould not be viewed as limiting however, as the described KERS systemsare designed for application with any two-wheeled or three-wheeledmotorcycle and other vehicle. Accordingly, in addition to any type ofmotorcycle, the KERS systems described may also be applied to scooters,mopeds, and other two-wheel or three-wheel motorized bikes or trikes.

The energy recovery system according to exemplary embodiments maycomprise a mechanical system, a hydraulic system, or a combinationthereof. The mechanical system will be referred to as the mechanicalKERS system. The hydraulic system will be referred to as the hydraulicKERS system.

Exemplary embodiments may include a front wheel system with certaingears and drive shafts located to convey energy starting at the frontwheel drive hub utilizing a sprag clutch, traveling along the frontforks, inside the lower triple clamp and steering head and then alongthe inside of the main frame of the motorcycle. In one embodiment, themechanical KERS system is constructed along both sides of the frontwheel and front forks. Alternatively, the mechanical KERS system may beconstructed only on one side of the front wheel and front forks. Infurther embodiments, a portion of the mechanical KERS system may even beconstructed and housed within one or both of the front forks. Thefollowing description provides an exemplary embodiment that includes amechanical KERS on both sides of the front wheel and front forks. Anadvantage of having the mechanical KERS system constructed on both sidesof the front wheel and front forks is that it can allow for balancing ofthe torque caused by the mechanical KERS system as it transfers powerfrom the front wheel to the motor shaft. Another advantage is theability to share the torque handling capacity by two sets of smallercomponents, e.g. two shafts and two gear sets, as opposed to using asingle large gear set and one heavy shaft. The use of a balanced KERSsystem that captures and transmits energy on both sides of the frontwheel and forks may be easier to install and operate in a safe mannerwith minimal impact on vehicle dynamics. Independent of whether themechanical KERS system is along one or both sides of the front wheel, byproviding the shafts and gears as described herein, it is possible tomaintain the aesthetic appearance of the motorcycle.

The basic structure of a motorcycle according to an exemplary embodimentequipped with the mechanical KERS system is shown in FIG. 1. Themotorcycle includes a main frame connected to a front wheel and a rearwheel via the front and rear suspension. The main frame houses andsupports the front and rear suspension, electric motor, motorcontroller, electronics, the electrical accumulator and all theancillaries. At the front portion of the frame, the triple clamps attachto the steering head portion of the frame. One or more handlebars may beconnected to the front fork that connects to the front wheel. Oppositethe handlebars and front fork are the swing arm and rear wheel. Theswing arm connects to and locates the rear wheel, which may be poweredby the electric motor by way a chain or a set of chains and a one waysprag clutch, also known as a one-way freewheel, or sprag bearing, thatallows the rear wheel to be driven by the electric motor in the forwarddirection and free wheel in the opposite direction.

In accordance with this general description, FIG. 1 shows a KERS systemequipped motorcycle 100 having a mechanical KERS system. The KERS systemequipped motorcycle 100 includes a frame 102, rear wheel 104 and a frontwheel 106 equipped with a one-way front wheel hub 108 that includes atleast one sprag clutch. The rear wheel 104 rotates about a rear wheelaxle 110 that is attached to swing arm 112. Swing arm 112 is attached toframe 102 at pivot point 118. The front wheel 106 rotates about a frontwheel axle 114 that is attached to front forks 116. Front forks 116attach to a lower triple clamp 126 and an upper triple clamp 128. Lowertriple clamp 126 and upper triple clamp 128 are rotatably attached to asteering head 120 located and integral to the front of frame 102. A lefthandlebar 130 and a right handlebar 132 are attached to front forks 116.Alternately, left handlebar 130 and right handlebar 132 may be attachedto upper triple clamp 128, or a single set of handlebars may be used.Left handlebar 130, right handlebar 132, upper triple clamp 128, lowertriple clamp 126, steering head 120, front forks 116, front wheel axle114 and front wheel 106 together form the steering assembly.

Frame 102 may include various combinations of frame tubing, bars, andother supporting members. The material and design of the frame shouldnot be viewed as limiting. Various materials may be used such as carbonfiber, titanium, steel, aluminum alloys, magnesium alloys orcombinations thereof.

Frame 102 will typically support the electric motor 122, an electricalaccumulator 124, a cooling system 134, and an electric motor controller136 among other components. The combination of an electric motor andelectric motor controller capable of electrical regeneration ispreferably used such as the PowerPhase® 145 Traction System manufacturedby UQM Technologies of Frederick, Colo. Electric motor 122 is rigidlymounted within frame 102 and electric motor controller 136 may bemounted within frame 102 or to a structural appendage mounted thereto.The frame may be designed to provide adequate strength and rigiditywhile minimizing the weight of the motorcycle. Importantly, the framemay be designed to properly distribute the weight of all the componentsand thus define the center of gravity of the motorcycle that has amarked effect on the overall handling of the motorcycle.

At the rear end of the frame is swing arm 112 with left and right armspivotally attached at opposite sides of the pivot point 118. In anotherexemplary embodiment, swing arm 112 may be replaced by a single-sidedswing arm (not shown).

The motorcycle may also include one or more shock absorber(s) 138pivotally attached between swing arm 112 and frame 102. Different typesof shock absorbers suitable for use with a motorcycle may beimplemented. For example, the shock absorber may include a damper unitwith a coil spring fitted around it such as produced by Ohlins, USA.

The rear wheel may be powered in different ways. In an exemplaryembodiment, shown in FIG. 1, electric motor 122 has a splined motorshaft 140. Motor shaft 140 is fitted with a motor drive sprocket 142that drives a jackshaft chain 152 that in turn drives a jackshaft inputsprocket 144 fitted to a jackshaft 146. Jackshaft input sprocket 144 ispreferably installed in conjunction with at least one sprag clutch thatallows the rear wheel to free wheel during coasting while the frontwheel mechanical KERS system is engaged. In this manner, the motorcyclemay be designed so that the front wheel and the rear wheel are notlocked together, thereby allowing the motor to harvest the kineticenergy from the front wheel without simultaneously powering the rearwheel. Jackshaft 146 rotates within jackshaft bearings 148 and is fittedwith a jackshaft output sprocket 150. Jackshaft output sprocket 150drives a rear wheel chain 154 that is connected to a rear wheel sprocket156 attached to rear wheel 104. In alternative embodiments, a driveshaft or chain may be used to transfer power directly from the motor tothe rear wheel without the use of jackshaft 146.

Using a jackshaft 146 as shown in FIG. 1, allows for better control ofthe gear ratio from the rear wheel to the motor shaft and can eliminatethe need for oversized rear wheel sprockets that are typically found onother electric motorcycle designs. By using a jackshaft, the size of therear sprocket may be reduced and gear ratios may be more preciselyadjusted. Also, using a jackshaft provides more discretion on thepositioning of the electric motor. A gear ratio may also be set betweenthe front wheel and the motor shaft. The gear ratios are critical to theproper function of a KERS system and for safety, as the front and rearwheels must not be locked together and forced to rotate at the samespeed through the selection of the incorrect gear ratios.

Front fork 116 may include two fork tubes held parallel to each other byupper and lower triple clamps 128 and 126. To provide forshock-absorbing suspension, the front fork may be a telescopic fork. Atelescopic fork consists of two fork tubes clamped into an upper and alower triple clamps 128 and 126 at their upper ends and to the frontwheel axle 114 at their lower ends. The upper and lower triple clampsare part of the steering assembly. The axle of the front wheel ispositioned between the fork tubes at the lower end. Each fork tube mayinclude an upper portion clamped to the upper and lower triple clampsand a lower portion or leg that slides into the upper portion. Manydifferent telescopic fork tube designs may be used. An exemplary forktube design may include a coil spring that allows the lower portion ofthe fork tube to slide into the upper portion of the fork tube. Bushingsbetween the lower portion of the fork tube and the upper portion of thefork tube may also be employed to minimize friction. Other known dampingarrangements may also be employed.

In addition to holding the fork tubes in place, in an exemplaryembodiment the upper triple clamp 128 may also support handlebars 130and 132 and be rotatably supported by steering head 120.

The front and rear wheels may be equipped with standard friction brakesystems. Different friction brake systems may be employed such as, butnot limited to disc brakes, drum brakes, or hydraulic brakes. The brakesmay be controlled by the rider using levers or switches mounted on thehandlebar. An advantage that may result from the KERS system inaccordance with exemplary embodiments is a more simplified brakingsystem. Regeneration using a KERS system harvests the energy from thefront wheel utilizing the energy that would otherwise have to bedissipated in heat by a front friction brake. In doing so, the KERSsystem effectively functions as a supplemental front brake whileallowing for the regeneration of energy. For this reason, application ofthe KERS system may also be referred to as “KERS braking” or“regenerative braking event,” and the torque applied to the motor duringemployment of a KERS system may be referred to as “regenerative brakingtorque.” Because of the additional braking that may be supplied by aKERS system, the implementation of a KERS system may result in lessfriction braking power necessary for the front wheel. In an embodimentusing disc brakes, for example, the vehicle may include a single discbrake as opposed to two disc brakes as the additional braking that wouldbe provided by the second disc brake may instead be supplied by the KERSsystem.

In accordance with exemplary embodiments, the front wheel mechanicalKERS system transfers power from the front wheel to the electricalaccumulator by transferring the kinetic energy from the front wheel tothe motor that can be controlled to become a generator by way of aregenerative braking torque effectuated by a motor controller. Themechanical KERS system may generally include one or two front shaftsthat turn when the front wheel is rotating in a forward direction. Thefront shafts extend vertically along the front fork and engage a mainshaft through a set of gears. The main shaft then extends inside themotorcycle frame and connects to a chain through a gear box. The chainultimately engages the motor shaft via a sprocket so that it can apply aload to the motor shaft. The load to the motor shaft is then used by themotor to generate power.

An illustration of an exemplary embodiment of the mechanical KERS systemis provided in FIGS. 1-6. In one embodiment, a portion of the frontwheel mechanical KERS system extends from the front wheel to thesteering head. As shown in FIG. 2, this portion of the mechanical KERSsystem may include a set of shafts and gears that are able to transferthe kinetic energy from the front wheel to the drive shaft. Themechanical KERS system front shafts 180 and 170 engage the front wheelwith a set of gears explained in further detail below. Although varioustypes of shafts can be used to implement the mechanical KERS system, theshafts used throughout the mechanical KERS system are preferably rigidshafts made of a light weight material. Using rigid shafts enables afull range of steering and instantaneous power transfer from the frontwheel to the motor with low friction. Typically, rigid shafts are veryefficient in transferring power and do not exhibit a rotationaldisplacement problem that can be present when using flexible shafts whensubject to a torque.

In an illustrative embodiment, this set of shafts and gears is locatedalong the front fork and outside the motorcycle shock-absorbing frontfork 116 with a first set of chains and sprockets optionally locatedinside the lower triple clamp 126. Alternatively, this portion of themechanical KERS system may instead be fully integrated within the frontfork 116 and the lower triple clamp 126.

To allow the motorcycle to still benefit from the shock absorption ofthe front fork 116, the mechanical KERS system may be designed toinclude telescoping front shafts 180 and 170 that can extend and retractvertically to accommodate the extension and retraction of the front fork116 while simultaneously transmitting full torque without binding. In anexemplary embodiment, the KERS system may include upper and lower frontshafts. In such an embodiment the lower shafts are guided using one ormore longitudinal races and ball bearings designed to allow the lowershafts to transfer torque to the upper shafts while at the same timebeing able to slide into the upper shafts when necessary to accommodatethe compression of the front fork.

At the steering head 120, the kinetic energy from the front wheel istransferred to a drive shaft 158 using a steering head mesh gear 190. Inan exemplary embodiment, the drive shaft 158 engages the gears in thesteering head using a bevel gear set located within the steering head.The motorcycle steering head gear 190 is preferably located within themotorcycle steering head 120 at or near the centerline of the motorcycle100 immediately behind the axis of steering of the motorcycle steeringmechanism. Positioning the motorcycle steering head gear 190 and thefront end of the rotating drive shaft 158 on the center line of themotorcycle 100 will result in minimal torque reactions that couldotherwise affect steering and control. Similarly, the upper steeringhead gear 188 and lower steering head gear 178 are located within themotorcycle steering head 120 at or near the axis of steering of themotorcycle steering mechanism to minimize or eliminate torque reactionsthat could affect steering and control. The steering head isstandard-size or, alternatively, enlarged in comparison to a standardmotorcycle to allow for full steering capabilities while transferringpower from the front wheel to the main shaft.

As shown in FIG. 1B, the drive shaft 158 extends from the steering headto a gear box 160 inside the motorcycle frame. The drive shaft 158should be firmly supported at both ends to enable free rotation, whilestill smoothly transferring of power from the motorcycle steering headmesh gear 190. In one embodiment, universal joints may be used toconnect drive shaft 158 with the various components. At the end oppositefrom the steering head 120, the drive shaft 158 engages a gear box 160.As shown in FIGS. 5 and 6A, the gear box 160 may be used to transferpower from drive shaft 158 to a sprocket engaged with KERS drive chain162. An advantage of using a gear box is the ability to transfer powerfrom the drive shaft 158 to the KERS drive chain 162 at an angle. Forexample, the angle may be 100 degrees allowing for more flexibility inthe design. The gear box 160 may then engage the KERS drive chain 162that extends to the motor shaft 140 engaging the motor shaft using amotor KERS drive sprocket 164.

FIG. 3 shows a detailed section view of the front wheel hub and itssubassembly. As shown in the exploded view on the left side of FIG. 3,front wheel hub 108 includes an axle 114, disc or brake rotor 200operatively engaged with caliper 202, axle bearing 204, drive hub 206,key(s) 208, and sprag clutch 210. Sprag clutch 210 can include one ormore internal bearings. In order to assemble the front wheel hub 108,the axle bearing 204 can be inserted into the drive hub 206. Next, drivehub 206 may be inserted into sprag clutch 210. When drive hub 206 isplaced inside of sprag clutch 210, one or more keys 208, such as squareor rectangular metal pieces, may then be inserted into the spacesbetween the assembly of the drive hub 206 and sprag clutch 210 in orderto lock the assembly together. The drive hub 206 and sprag clutch 210assembly can then be placed inside of clutch housing 214 which holds thedrive hub 206 and sprag clutch 210.

Clutch housing 214 may be integral to wheel 220 or fastened to wheel 220using one or more screws, bolts, etc. Referring now to the right side ofFIG. 3, the drive hub 206 may then operably engage a ring gear 216. Ringgear 216 may then operably engage pinion gear 218 which turns one of theKERS system front shafts.

To complete the front wheel hub 108, a disc or brake rotor 200 may beplaced in between the front fork 116 and the assembly of drive hub 206and sprag clutch 210 that resides in clutch housing 214. One or morescrews, bolts, etc. may be used to fasten the disc or brake rotor 200 tothe clutch housing 214.

Referring now to both FIGS. 2 and 3, when the front wheel 106 isassembled, power is transferred from the front wheel 106 to theelectrical accumulator using a front shaft 180 and a front shaft 170located along the front fork 116. The front wheel hub 108 may beequipped with sprag clutch 210 that allows the front wheel to free-wheelin one direction and engage the mechanical KERS system in the oppositedirection. Using a sprag bearing or sprag clutch 210 at the front wheelhub 108 allows the front wheel 106 to transfer the kinetic energy whenengaging the mechanical KERS system, while preventing the front wheel106 from being driven by the motor 122. In other words, using a spragclutch 210 prevents power transfer from the motor 122 to the front wheel106, such that the motorcycle 100 is rear-wheel drive.

As will be described in further detail with respect to FIGS. 6A-6C, 7,and 8A-8B, by using sprag clutches that allow the front 106 and rear 104wheels to free wheel in one direction, it is possible to operate thefront wheel 106 mechanical KERS system independently and separately fromthe powering of the rear wheel 104. In this manner, the front wheel 106is not powered by the motor 122 and the rear wheel 104 is not locked inwith the mechanical KERS system.

To transfer the kinetic energy, the front wheel 106 engages each offront shafts 170 and 180 using a gear system such as a ring and piniongear as described above, a hydraulic coupling, a roller clutch, aratchet clutch, or hub clutch. Additionally, the front wheel hub 108 mayoptionally include a torque-limiting clutch to enable release of extremetorque loads. For illustrative purposes only, the present applicationdescribes an exemplary embodiment in which the mechanical KERS systemincludes ring 216 gear and pinion gear 218 on each side of the frontwheel to connect the front wheel 106 to front shaft 180 and front shaft170 of the mechanical KERS system.

Once front shafts 180 and 170 are engaged with the front wheel, theytransfer power through a set of shafts generally located along oroptionally within the front fork 116, and within the steering head 120and motorcycle frame 102. The shafts 180 and 170 may be held in placeusing bearings or bushings at either or both ends. Different bearings orbushings keep the shafts 180 and 170 in place while allowing for freerotation and for vertical movement of the front shafts 180 and 170 sothat the mechanical KERS system is able to adjust for the movement ofthe shock-absorbing system of the front fork 116 while transferring thekinetic energy from the front wheel 106 to the steering head 120.

When engaged, the front shafts 180 and 170 may be designed to rotate inopposite directions. This may lead to a better counter balance of thetorque created by their motion. At their upper ends, the front shafts180 and 170 engage gears or chains and sprockets located in the lowertriple clamp 126. These gears or chains and sprockets then transmitpower upward through the steering head 120 as explained in more detailbelow.

In an exemplary embodiment, the KERS front shafts 170, 180 operativelyengage the sprockets 173 and 183 respectively within the lower tripleclamp 126. Different methods may be used to operatively engage frontshafts 170 and 180 with sprockets 173 and 183, for example the shaftsmay include a splined surface at least on an upper end thereof;alternatively, they may have a square or other design that fits insidethe sprockets. The upper end of the front shaft 170 slides into andpowers lower triple clamp sprocket 173, and the upper end of front shaft180 slides into and powers lower triple clamp sprocket 183.

As shown in FIGS. 2 and 4, the lower triple claim 126 may be equippedwith a first series of triple clamp sprockets 184, 183 that drive aninner tube 186 via chain 182 and a second series of meshing triple clampsprockets 174, 173 drive an outer tube 176 via chain 172. Although inthe illustrated exemplary embodiment the lower triple clamp 126 isequipped with four sprockets and two chains, the number of sprockets andchains employed should not be viewed as limiting. Sprockets 183 and 173are engaged by the upper portions of front shafts 180 and 170respectively. Chain 182 operatively engages sprocket 184 and sprocket183, while chain 172 operatively engages sprocket 174 and sprocket 173.Sprockets 183, 184, 173, and 174 may be sprockets or any other type ofgear that may be engaged with chains. In this manner, as the front shaft180 turns sprocket 183 it turns chain 182 that turns sprocket 184.Similarly, as the front shaft 170 turns sprocket 173 it turns chain 172that turns sprocket 174. The gears powered by the shaft 180 may rotateindependently from those engaged by the shaft 170. This may be achievedby aligning the gears and chains on different planes as shown in FIG. 2.Specifically, in an exemplary embodiment, sprockets 183, 184, and chain182 are located on one plane while sprockets 173, 174 and chain 172 arelocated on a different plane either above or below the plane on whichsprockets 183, 184, and chain 182 are located. This may also preventinterference between the operation of the two sets of sprockets andchains. Like the front shafts 170 and 180 described above, sprockets184, 183 and chain 182 may rotate in the opposite direction thansprockets 174, 173 and chain 172. This counterbalances the torque withinlower triple claim 126.

Lower triple clamp 126 holds lower triple clamp sprockets 184, 183, 174,and 173 and chains 172, 182 in a fixed position with support bearingsprotecting the rider and allowing free rotation. The arrangement andnumber of these gears is not limited to a specific set. Numerousalternate gear combinations may be used for transmitting power from thefront portion of the mechanical KERS system to the drive shaft 158. Forexample, the front fork designs may employ the use of expanding ballspline universal joints in the place of the sprockets and chains 172-174and 182-184. Also, lower triple clamp sprockets 184, 183, 174, and 173may include different types of gears with different designs such asspiral design, straight teeth, or any other suitable gear design knownto one of ordinary skill in the art. For example, helical gears may beused for their strength, smoothness and quieter power transfer.

In an exemplary alternative embodiment, instead of using a chain andgear combination, the power from the front shafts 170 and 180 may betransferred to inner and outer front tubes 186 and 176 by a set ofmeshed gears. In this manner, as the front shafts 180 and 170 rotate,they rotate the first gear they each engage in the lower triple clamp126. Those gears will in turn transfer power to other gears meshedthereto that can in turn transfer power to other gears meshed theretountil the gears connected to inner and outer tubes 186 and 176 arereached. Like the gear and chain arrangement discussed above, a meshedgear arrangement may also be designed to work on two planes so that thegears powered by front shaft 170 do not impede movement of the gearspowered by front shaft 180.

As shown in FIGS. 2 and 4, inner sprockets 184 and 174 are engaged to aninner front tube 186 and an outer front tube 176 respectively. The innerand outer front tubes 186 and 176 are used to transfer the power fromthe lower triple clamp gears to the drive shaft 158. The gears orsprockets can be made to engage the inner and outer tubes 186 and 176using different designs. In one exemplary embodiment the invention usessupport bearings that allow the inner and outer tubes 186 and 176 to berotated by the inner gears or sprockets located in the lower tripleclamp 126. The inner and outer front tubes 186 and 176 may be alignedalong the steering axis and may be supported on bearings located in thesteering head 120 and the upper triple clamp 128. In this manner they donot restrict or hinder steering of the motorcycle 100.

With continued reference to FIGS. 2 and 4, inner and outer front tubes186 and 176 may extend into the steering head that may include mesh gear178 attached to and powered by the outer tube 176, mesh gear 188attached to and powered by inner tube 186, and mesh gear 190 engaged andpowered by mesh gears 178 and 188. Mesh gear 190 may also be connectedto drive shaft 158 to transfer the power from inner and outer fronttubes 186 and 176 to drive shaft 158. In this manner, the combinedrotational power of inner and outer tubes 186 and 176 may be transferredto drive shaft 158 by way of mesh gear 190. Mesh gears 178, 188, and 190are not limited to a particular design. In an exemplary embodiment,these gears are bevel edge gears. To accommodate these gears, thesteering head 120 preferably has a cut away section in the center. Also,the steering head 120 is designed to act as a gear casing locatedbetween the upper ends of the fork members and below the handlebars 130and 132. This is done by designing the cut away to create two sectionssupported by needle bearings within the steering head 120 and byclamping power of the upper and lower triple clamps 128 and 126 aboveand below the steering head 120 so as not to interfere with rotation ofthe handlebars 130, 132 and fork members.

As with the gears in the lower triple clamp 126, gears 178 and 188 maybe designed to rotate in opposite directions to help counterbalance therotational torque inside the steering head 120. Drive shaft 158 isthereby rotated using gear 190 located at its front end and engaged withmesh gears 178 and 188.

At the opposite end from the steering head 120, drive shaft 158 engagesa gear box 160 that engages a KERS drive chain 162. The KERS drive chain162 runs from the gear box 160 to the motor shaft 140. Accordingly, asthe drive shaft 158 transfers the rotational power from inner and outertubes 186 and 176, it engages gear box 160 and causes KERS drive chain162 to rotate. As the KERS drive chain 162 rotates it turns a sprocketlocated on the motor shaft 140. In engaging the sprocket, KERS drivechain 162 induces a load to the motor shaft 140 that is then used by theelectric motor to generate electrical energy that may be transferred tothe electrical accumulator.

The motor is not limited to a specific design. In an exemplaryembodiment, the motor is a liquid-cooled electric motor with instanttorque response that is able to provide 194 horsepower. However, evenmore or less powerful motors may be employed.

As discussed previously in conjunction with exemplary embodiments, thefront wheel of the vehicle may be operatively engaged to the motor shaftusing a series of gears and/or sprockets. Similarly, the rear wheel maybe operatively engaged to the motor shaft using a series of sprocketsand/or gears. As explained in more detail in the following paragraphs,these gearing systems between the motor shaft that the front and rearwheels may be designed to obtain desired gear ratios and to obtain adifferential system that allows the front and rear wheels to rotate atvarying relative speeds.

FIGS. 6A-6B illustrate partial front and rear views of a KERS system ina motorcycle. In an embodiment, motorcycle 100 includes a sprag clutchhousing 222, a portion of a steering head 120 of the motorcycle frame,shafts and universal joints, such as jackshaft 146, jackshaft outputsprocket 150, an upper gearbox 160, chains, motor shaft, and electricmotor mounting plates.

Moving now to FIG. 6C, a cross-sectional view of the jackshaft of FIG.6B where the rear wheel sprag clutch housing 222 may be located isillustrated. As shown, sprag clutch housing 222 includes a sprag clutch224. Although sprag clutch housing 222 as illustrated includes one spragclutch 224, multiple sprag clutches may be used depending on the amountof torque applied and torque capacity of the sprag clutches used. Asfurther depicted, jackshaft 146 includes a jackshaft input sprocket 144,jackshaft bearings 148, and jackshaft output sprocket 150. In theillustrated embodiment, as jackshaft 146 rotates within jackshaftbearings 148, it turns jackshaft output sprocket 150. When jackshaftoutput sprocket 150 is turned, the rear wheel chain (not shown)transfers power to the rear wheel 104. Although a specific number ofsprockets and gears are depicted, a person of skill in the art willappreciate that any number of sprockets and/or gears may be used.

FIG. 7 is an additional top down view of the layout of a portion of aKERS system in an electric motorcycle including the electric motor,motor shaft, jackshaft, chains, and drive sprockets. In the illustratedembodiment, motorcycle 100 includes electric motor 122, motor shaft 140,motor drive sprocket 142, jackshaft input sprocket 144, jackshaft 146,jackshaft bearings 148, jackshaft output sprocket 150, jackshaft chain152, rear wheel chain 154, KERS drive chain 162, and KERS drive sprocket164.

As described above, if the drive and regenerative braking torques are tobe provided by the same device (e.g., electric motor 122) in a KERSsystem equipped motorcycle 100, then a system and method fortransferring torque between the device and both wheels is needed. Asdiscussed, the front wheel 106 and rear wheel 104 of motorcycle 100 maybe connected to the motor 122 directly through the drive trains of gearsand chains. Unfortunately, connecting both front and rear wheels 106 and104 to a single device (e.g., electric motor 122) may result ineffectively connecting both front and rear wheels 106, 104 together andresult in the front and rear wheels 106 and 104 being forced to alwaysspin at the same rate.

The wheels of motorcycles, however, often rotate at slightly differentspeeds under varying conditions, e.g., acceleration vs. deceleration,front tire wear vs. rear tire wear, different tire radii due to leanangles during turns, etc. Forcing the wheels of a motorcycle to spin atthe same speed can cause at least one tire to slip, resulting in rapidwear and potentially dangerous loss of traction.

For example, when a rider of motorcycle 100 leans during cornering, theradii of the front and rear wheels 106 and 104 may be reduced due to theprofile of rear tires commonly made today. However, because of theirdesign the front wheel radius may change less than the rear wheelradius. If the radius of the front wheel 106 changes more quickly thanthe radius of the rear wheel 104 a rider may lose control whenmotorcycle 100 is leaning if the wrong gear ratios are used between themotor 122 and front wheel 106, relative to the gear ratios between themotor 122 and the rear wheel 104.

As previously discussed, the disparity between front and rear tire wearcan also be attributed to the large accelerations and decelerations thatare associated with motorcycle racing. For example, when a motorcyclelifts up during a state of acceleration (e.g., wheelies) or the rearwheel of the motorcycle lifts up during a state of braking, rapidchanges of the radii of the front and rear wheels 106 and 104 occurs.

Although traditional passive differentials that are employed inautomotive technology, such as 4 wheel-drive (4WD) cars, can be used toovercome the foregoing problems, they may not be suitable formotorcycles. In particular, such passive differentials are not suitablefor environments where there is torque split between the wheels that isnot constant. Because motorcycle applications require the majority ofthe torque to be sent to the rear wheel during acceleration and themajority of the torque to be absorbed from the front wheel duringbraking (i.e., a non-constant torque split), conventional automotivedifferential systems may not be appropriate.

To overcome these and other problems described herein, a dead zone maybe created that allows the front 106 and rear 104 wheels to spin atdifferent speeds. A dead zone may be created by using sprag clutches 224and 210 and selecting appropriate gear ratios for the front and rearwheels 106 and 104. Sprag clutches enable front 106 and rear 104 wheelsto free wheel in one direction and operate independently of the motor122 and/or mechanical KERS system. The use of sprag clutches andselection of appropriate gear ratios allow motorcycle 100 to be riddensafely.

Applicants have also discovered a method to determine the appropriatefront and rear wheel gearing to create the desired dead zone. Inparticular, when sprag clutches such as rear sprag clutch 224 and frontsprag clutch 210 are employed in motorcycle 100, the method may be usedto select the number of teeth to utilize on the various sprockets andgears of motorcycle 100 to achieve the appropriate gear ratios betweenthe electric motor and the front and rear wheels 106 and 104 as shown inthe derivation below.

This method is derived below as a rule for the minimum gear ratiobetween the rear wheel 104 of motorcycle 100 and the motor 122 in orderto prevent the front and rear wheels 104, 106 from locking up. As usedin the derivation below, “v” represents the vehicle speed (in/s), “R”represents wheel radius (in), “r” represents effective gear pitch radius(in), “w” represents angular velocity (rad/s), and “s” represents slipratio (non-dimensional). Slip ratio is defined in Equation (1).s=((w×R)/v)−1  Equation 1:Typical values for “s” during maximal acceleration range from +0.10 to+0.20. Typical values during maximal deceleration range from −0.10 to−0.20.

In the following derivation, the subscript “r” represents rear, “f”represents front, and “m” represents motor. Applying Equation 1 to thefront and rear wheels and solving for vehicle speed so it can later beeliminated yields Equations (2) and (3).v=w _(r) ×R _(r)/(1+s _(r))  Equation 2:v=w _(f) ×R _(f)/(1+s _(f))  Equation 3:Combining Equation (2) and Equation (3) to eliminate vehicle speed andsolve for front wheel speed in terms of rear wheel speed yields Equation(4).w _(f)=(R _(r) /R _(f))×((1+s _(f))/(1+s _(r)))×w _(r)  Equation 4:

The sprag clutch on the rear wheel enforces Equation (5), and the spragclutch on the front wheel enforces Equation (6).w _(m) ×r _(m) ≦w _(r) ×r _(r)  Equation 5:w _(m) ×r _(m) ≧w _(f) ×r _(f)  Equation 6:

Substituting Equation (4) into Equation (6) to express it in terms ofrear wheel speed instead of front wheel speed, then rearranging Equation(5) and (6) to show the limitations on the desired gear ratio,w_(m)/w_(r), yields Equation (7).(r _(f) /r _(m))×(R _(r) /R _(f))×(1+s _(f))/(1+s _(r))≦w _(m) /w _(r)≦r _(r) /r _(m)  Equation 7:Equation (7) can only hold if Equation (8) is true in all circumstances(r _(r) /r _(m))≧(r _(f) /r _(m))×(R _(r) /R _(f))×(1+s _(f))/(1+s_(r))  Equation 8:This worst-case condition is expressed in Equation (9)(r _(r) /r _(m))≧(r _(f) /r _(m))×(R _(r) /R _(f))_(max)×((1+s_(f))/(1+s _(r)))_(max)  Equation 9:Equation (9) is the minimum gear ratio rule the applicants have derivedto ensure the front and rear wheels do not lock up, that some dead zoneis present. Alternately, the rule can be expressed in terms of the frontgear ratio, as shown in Equation (10)(r _(f) /r _(m))≦(r _(r) /r _(m))*(R _(f) /R _(r))_(min)*((1+s_(r))/(1+s _(f)))_(min)  Equation 10:

Using equation (10) above, a default of rear gear ratio, r_(r)/r_(m), of4.68639, and a worst-case wheel radius ratio, R_(f)/R_(r), of11.91/12.78, the required front wheel gear ratio, r_(f)/r_(m), can bederived. For simplicity in the example, we will assume that braking isonly done with the front wheel, so s_(f)≦0 and s_(r)≧0, and thus theworst-case slip term in Equation (10) is 1. The above parameters wouldresult in the following:(r _(f) /r _(m))≦(4.68639)×(11.91/12.78)×1(r _(f) /r _(m))≦4.3674In practice, some rear wheel braking should be accounted for with aslightly negative rear slip ratio s_(r). A person of skill in the artwill appreciate that the slip term in equation (10)((1+s_(r))/(1+s_(f)))_(min) may be less than 1. Thus, an even smallergear ratio would be required.

Accordingly, for gear ratio (r_(f)/r_(m)) to equal 4.3674, motor drivesprocket 142 would need to have 13.05 teeth. However, an integer numberof gear teeth are needed. Because a gear ratio (r_(f)/r_(m)) of lessthan 4.3674 is desirable, it would be preferred to have 14 teeth (e.g.,a 7.27% dead zone) on motor drive sprocket 142. A person of skill in theart will appreciate that any number of teeth greater than 14 (e.g., 15teeth—a 14.94% dead zone) may be used as long as minimum gear ratio usedin rear wheel 104 is satisfied. Additionally, depending on the gearratio and wheel radii utilized, varying numbers of teeth may be used onmotor drive sprocket 142 using the method described herein. Of note, thecombination of all the sprockets yields the gear ratio. Thus, dependingon the gear ratio and wheel radii utilized, varying numbers of teeth maybe used on motor drive sprocket 142 and/or other sprockets using themethod described herein. Of note, in some embodiments, an electronicallycontrolled (e.g., active) differential may be used in place of or incombination with one or more sprag clutches.

Furthermore, as previously described the jackshaft can be used to reducethe gear ratio between motor drive sprocket 142 and rear wheel sprocket156 attached to the rear wheel. For example, the total gear ratiobetween the electric motor and the rear wheel may be 4.68 to 1, achievedwith the following sprockets: 13-tooth motor drive sprocket, 18-toothjackshaft input sprocket, 13-tooth jackshaft output sprocket, and44-tooth rear wheel sprocket. The gear ratio is not limited to 4.68 andmay be modified to obtain the desired performance.

FIGS. 8A-8B illustrate graphical representations of a “dead zone”created by the use of front and rear wheel one-way sprag clutches incombination with appropriate gearing between the front and rear wheelsand the motor shaft. By allowing a slight dead zone it is possible toprevent the torque from the mechanical KERS system from being applied tothe rear wheel 104 and to prevent the acceleration torque from the rearwheel 104 being applied to the front wheel 106. This can advantageouslyprevent locking of the front and rear wheels 106, 104 and loss ofcontrol of motorcycle 100.

Although one-way sprag clutches, such as front sprag clutch 210 and rearsprag clutch 224, may be used, a person of skill in the art willappreciate that other clutch types and gearing may be used. In someembodiments, the one-way sprag clutches may be combined with othergearing of the front and rear wheels 106, 104. For example, sprocketsand teeth numbers, clutches, sprag bearings, associated gearing,clutches, etc. can be arranged to allow for the dead zone.

FIG. 8A illustrates operation of a one-way sprag clutch, such as rearsprag clutch 224 that may be utilized to selectively apply torque to therear wheel 104 of motorcycle 100. Applicants have discovered that animproved way to transfer acceleration torque to the rear wheel 104, butnot braking torque, is to use a one-way clutch, e.g., an over-runningclutch, free-wheel clutch, sprag clutch, etc. A one-way clutch canadvantageously allow the rear wheel 104 to spin more quickly than themotor 122, but not more slowly. Thus, when the motor 122 tries to spinfaster than the rear wheel 104, it engages the clutch, and transferstorque to the rear wheel 104 that accelerates the motorcycle 100.Likewise, another one-way clutch can be used in the other direction inorder to transfer only braking torque from the front wheel 106.

With continued reference to FIG. 8B, a differential system that includesthe combined operation of two one-way sprag clutches, such as frontsprag clutch 210 and rear sprag clutch 224, on front wheel 106 and rearwheel 104 is shown. As can be seen, a slight dead zone allows the frontand rear wheels to spin at slightly different speeds. Advantageously,the gearing such as the number of teeth can be selected so that there isa slight dead zone, allowing the front and rear tires to spin atvariable speeds. This allows the front and rear wheels 106,104 to freewheel in one direction and/or operate the front wheel 106 mechanicalKERS system independently and separately from the powering of the rearwheel 104. In this manner, the front wheel 106 is not powered by themotor 122 and the rear wheel 104 is not locked in with the mechanicalKERS system. During acceleration, the motor 122 spins faster than thewheels, and thus the rear wheel sprag bearing may be engaged while thefront wheel sprag bearing is disengaged and overrunning. When the riderdecelerates, the motor 122 slows down, disengaging the rear wheel spragbearing and engaging the front wheel sprag bearing. Notably, such a deadzone feature can also be used in an opposite transition to acceleration.

In an embodiment, during acceleration the motor 122 may be trying tospin faster than the wheels, and thus the rear clutch may be engaged andthe front clutch is disengaged. This acceleration process is shown asthe dark solid line in the FIG. 8B. Thus, when the rider begins brakingthe motor slows down, the rear clutch is disengaged, and the frontclutch is engaged. This process is depicted by the dark shaded line. Asbraking continues, the motor 122 continues to try to spin slower thanthe front and rear wheels 106, 104, keeping the front clutch engaged andthe rear clutch disengaged. This process is shown as the darkdash-dotted line. Due to constant leaning by motorcycle riders, thethreat of a loss of control that would occur without such a dead zone isquite high in road environments, thus having a dead zone can greatlyimprove motorcycle safety. And although dirt environments may not posequite as large a risk because of reduced leaning and because dirt ismore forgiving to locked wheels than pavement, a dead zone may still beemployed to improve safety in such environments as well.

In addition to having an appropriate gearing system, exemplaryembodiments may also include a control system for the KERS system andthe other components of the vehicles. As discussed previously, duringregenerative braking events, the KERS system may cause front wheelbraking that slows the vehicle while charging the electricalaccumulator. This feels like front wheel friction braking to the rider,however, in some situations such as when the electrical accumulator isin a state of high charge, full braking by the KERS system may not beachieved and thus a conventional friction braking system on the frontwheel is desirable. With respect to the front wheel, the front frictionbrake system can work together with or independently of the KERS system.When operated at the same time, the KERS system may be engaged before,after, or simultaneously with the front friction brake. In oneembodiment, the KERS system and the friction brakes are independentlycontrolled by the rider. In this manner, the rider has full control ofthe application of both the friction brake and KERS system that alsoprovides for braking. This allows experienced riders to apply the rightbalance of braking depending on the situation. For example, going arounda turn at a high speed the rider may desire to have full control as tothe application of the friction brake and/or KERS system to achieve bestperformance. In an exemplary embodiment, the handlebar may include afirst lever to engage the front friction brake and a second lever toengage the KERS system that applies additional braking.

Alternatively, the KERS system may be made to engage automatically, i.e.the KERS system control may be integrated into the friction bakingsystem. In such a system, an engine control unit (ECU) may be programmedto determine the appropriate application of the KERS system based on theamount of braking pressure applied by the rider such as via brake fluidpressure sensor as well as other information it receives as discussedabove. The system may also be designed to include a combination ofmanually operated and automatic engagement of the KERS system. In thislatter embodiment, the rider would have the option to choose whether toengage the automatic system or manual system, or use a proportion ofboth, via a switch that may be located on the handlebar. Alternatively,the switch could adjust the ratio of friction braking to the brakingprovided by the KERS system.

The rider can choose when to engage the KERS system using a control. Thecontrol may be a switch, a potentiometer, a push button, a lever, acable or any similar engagement device. In the exemplary embodimentshown in FIG. 9, the control is shown as a rotary position potentiometeractuated by a KERS brake lever 166. In alternative embodiments, therider can choose when to engage the KERS system in an automated mode byachieving the desired amount of braking with a combination of the KERSsystem and front friction brakes.

An exemplary embodiment of a KERS brake lever and KERS position sensoris provided in FIG. 9. In this embodiment, the KERS brake lever 166 isconnected to a KERS position sensor 230 by way of a steel cable 226 anda rotary cam with a return spring 228. In an alternative embodiment theposition sensor may be provided on the handlebar, proximate the KERSbrake lever 166. In an exemplary embodiment, the KERS position sensormay be designed to send a signal from 0 to 5 V to the ECU based on theamount of pressure the rider exerts on the KERS brake lever 166. Inother words, the KERS position sensor may be designed to send 0V whenthe KERS brake lever is not being operated and as high as a 5V signal tothe ECU when the KERS brake lever is fully squeezed.

In one exemplary embodiment the throttle position sensor is designedsimilarly to the KERS position sensor. In other words, the throttle onthe handlebar is connected to a throttle position sensor by way of acable and a rotary cam with a return spring. The throttle positionsensor then sends a signal to the ECU based on the degree of twist ofthe throttle on the handlebar.

An engine control unit (ECU) may be used to control and monitor theoperation of the motorcycle. The ECU can detect and control the loadthat a KERS system provides to the electrical accumulator and thusprevent damage to the electrical accumulator due to over charging. TheECU can also control the braking done by the disc brakes in the frontwheel for a comprehensive “brake-by-wire” solution. As described in moredetail below, the ECU may be designed to receive a series of informationsuch as speed, electrical accumulator voltage, remaining length of thetrip, lean angle and other such information collected by a series ofsensors located on the motorcycle and/or inputted by the rider. Based onsuch information, the ECU may then determine the appropriate level ofregenerative torque to apply to the electric motor.

It should be recognized that various designs of control units andsensors can be used and thus no particular design should be viewed aslimiting. In one embodiment, a series of inertial sensors and/or chassissensors feed information to an ECU. In an exemplary embodiment, the ECUmay be connected to a motor controller and to a rider dashboard display.The connection between the ECU and the motor controller may beaccomplished by way of a user-configurable controller-area network bus194 (CAN network bus). The motor controller may be designed tocommunicate with the electrical accumulator and with the electric motor.Additional sensors may also be connected to the motor to improveoperational control. In an alternative embodiment, the ECU and motorcontroller may be combined into a single device thus avoiding the needfor using CAN networks. In such an embodiment, the single ECU/motorcontroller device would perform all the functions of the ECU and motorcontroller described herein. CAN network busses may also be used toconnect the ECU to other components on the vehicle such as, for example,the rider dashboard display, a global positioning system (GPS), dataacquisition system, and other similar types of electronics.

An exemplary flowchart of the interconnection between the ECU, motorcontroller, rider dashboard display, and various sensors is provided inFIG. 10A. In this embodiment, the ECU is shown to receive informationfrom the chassis and inertial sensors that measure one or more of thefollowing: speed of the vehicle, front and back brake pressure, frontand back wheel speed, front and back suspension travel, GPS informationsuch as position of the vehicle relative to its intended destination,lap timer, attitude heading and reference system (AHRS). The AHRS isable to provide information relating to the position of the bikerelative to a reference plane such as the horizon, for example leanangle and tilt. In addition to the information from the chassis sensors,the ECU also receives information from a KERS position sensor, athrottle position sensor, a battery management system and the motorcontroller.

Based on the information received, the ECU can then determine theappropriate KERS control, state of the electrical accumulator, andcalculate a race finishing algorithm. In determining the appropriateKERS control, by taking into account the full set of conditions, the ECUmay also be designed to override the rider's command and limit theamount of regeneration. For example, in a situation in which the vehicleis at large lean angle, which may be communicated to the ECU by theAHRS, the ECU may fully or partially override a rider's command to startregeneration to that would otherwise present a hazardous condition. Asdiscussed above, the ECU outputs signals to the rider dashboard displayand the motor controller and in some embodiments, the ECU may generateother outputs.

The ECU may be made to communicate with the rider dashboard display andthe motor control with the use of CAN networks. The information sharedbetween the ECU and motor controller may include revolutions per minute(RPM), temperature, voltage, amperage, positive torque command foracceleration, and regenerative braking torque commands for regenerationby the KERS system.

The motor controller is also not limited to a particular design. In anexemplary embodiment, the motor controller has a 500 Amp input currentlimitation, however, more or less powerful control units may beemployed. As stated above, the motor controller, based on theinformation received from the motor, electrical accumulator, and/or theECU, controls the torque in the motor and thus the energy regenerated bythe motor.

As shown in FIG. 10A, in addition to the ECU, the motor controller isalso connected to the electrical accumulator and to the electric motor.The motor controller monitors the temperature and RPM of the electricmotor and based on the commands from the ECU, initiates positive torqueor regenerative braking torque in the electric motor.

To prevent damage to the motor controller and electric motor, anexemplary embodiment may also be equipped with a coolant system. Anexemplary coolant system may include two radiators and a coolant pump.In the example shown in FIG. 10, a coolant pump forces a coolant fluidto circulate through a first radiator, the motor controller, a secondradiator, and the electric motor.

The electrical accumulator may include any type of rechargeableelectrical accumulator. Exemplary rechargeable electrical accumulatorsinclude batteries. Various battery or battery packs may be used.Preferably the batteries used will be light weight and highly efficient.The type of battery used depends on the type of vehicle beingconstructed, i.e. a street vehicle or a racing vehicle among otherfactors such as cost and size. Other exemplary rechargeable electricalaccumulators are capacitors that can be constructed in various ways. Inaddition to being connected to the motor controller, the electricalaccumulator is also connected to the battery management system that, asexplained above, feeds information to the ECU. The electricalaccumulator and the battery management system may also be equipped witha shore power component that may be used for charging. An exemplaryshore power component would be a plug designed to connect to an externalpower source to power an of-board battery charger. Additional sensorsmay also be employed in the shore power and battery charging componentsto monitor the state of the electrical accumulator, such as temperature,individual cell voltage, and current fed to the charger. Finally, toprevent the electrical accumulator from overheating, it is preferable toalso include a cooling system, such as a ram air cooling system that canprovide for forced air convection to cool the electrical accumulator.The ram air cooling system may include ducts that extend from the frontof the motorcycle where they collect high pressure air and extend towhere the electrical accumulators are located.

During operation the user will operate the throttle to accelerate andthe KERS brake lever during braking. As shown in exemplary FIG. 10B,when the rider operates the throttle, the throttle position sensor sendsa signal to the ECU. Based on the signal from the throttle positionsensor, along with one or more other signals such as speed of thevehicle, ramp profile, maximum allowable motor RPM, and maximum torquetable, the ECU determines the amount of torque required by the electricmotor to achieve the desired acceleration. The ECU then may output asignal to the motor controller to power the electric motor and initiatethe required torque to accelerate the speed of the vehicle. To theextent a smoother transition into acceleration mode is desired, the ECUmay adjust the generation of torque based on the speed of the vehicleand achieve an almost seamless transition into acceleration. The motorcontroller powers the electric motor to generate the required torqueusing the energy from the electrical accumulator. During this operation,therefore, the energy stored in the electrical accumulator may decrease.

During deceleration, instead, in an exemplary embodiment the rider wouldoperate a control device such as the KERS brake lever. As shown inexemplary FIG. 10C, when the rider operates the KERS brake lever, theKERS position sensor sends a signal to the ECU. Based on the signal fromthe KERS position sensor, along with one or more other signals such asspeed of the vehicle, ramp profile, and speed of the front wheel, theECU determines the amount of regenerative torque in Nm to initiate inthe electric motor. The ECU may then output this regenerative torquecommand to the motor controller, which initiates regenerative brakingtorque in the electric motor to decelerate the vehicle whileregenerating power for the electrical accumulator. In order to achieve asmoother transition from acceleration to regeneration mode, the motorcontroller may also be commanded by the ECU to initially initiate atorque in the electric motor to match the speed of the front wheel andthen to effectuate regenerative braking torque in accordance with thecommand from the ECU once the speeds are matched. As the motor appliesthe regenerative braking torque it regenerates electricity that themotor controller can then send to the electrical accumulator. As such,during this operation energy in the electrical accumulator may berestored.

As explained above, operation of the KERS brake lever may in effectdecelerate the motorcycle. As such, use of the KERS system may act as abraking system. Upon operation by the rider, the KERS brake lever mayprovide a linear signal to the ECU. Using an unaltered linear signaloutput from the KERS brake lever, however, may make it difficult for therider to manually control the application of KERS system. In otherwords, if the KERS brake lever were to be squeezed too suddenly, alinearly correlated regenerative braking torque command may result in anundesired abrupt braking that may result in locking of the front wheeland loss of control. To soften the onset of the regenerative brakingcommand, which may be desirable when the KERS brake lever is squeezedabruptly, the ECU may be designed to output a non-linear responsedespite a linear input from the KERS position sensor.

A comparative example of the operation of a vehicle in which an ECUoutputs a linear vs. non-linear regenerative torque command is shown inFIG. 11. A plot of the regenerative torque command versus the commandfrom two 0 to 5 V KERS position sensors is provided in FIG. 11. Asshown, when the KERS brake lever is fully squeezed and the KERS positionsensor sends a 5 V signal to the ECU in both the linear and non-linearmodels the maximum regenerative torque command in Nm will be the same,i.e. 200 Nm. However, at a 1.5 V command, in a linear model theregenerative torque command for a linear model is 60 Nm while for anon-linear model it is approximately 28 Nm. Accordingly, using thenon-linear model, at 1.5 V KERS position sensor command, the rider wouldexperience half as much braking force than a rider using a linear model.

An advantage of the KERS system in accordance with exemplary embodimentsis the ability to model its operation to obtain superior performancefrom an electrical accumulator as well as to determine the suitabilityof a candidate electrical accumulator for use with a front wheel KERSsystem based on how the electrical accumulator will respond underextreme charge and discharge cycles. This may be achieved by modelingthe operation of the KERS system based on a given set of conditions thatreflect a desired vehicle performance and by testing the electricalaccumulator using a set of calculated current levels and durations for aset of desired duty cycles from a series of discharge and energyrecovery events. An exemplary embodiment demonstrating how the operationof a KERS system may be modeled after a set of given conditions isprovided below in conjunction with FIGS. 12A and 12B.

FIG. 12A is series of two plots showing the charge obtained using a KERSsystem and discharge current profile over the course of onerepresentative lap of a representative racetrack. The positive numberson the Y-axis above zero represent current in amps that will be drawnfrom the electrical accumulator during acceleration with a scale of zeroto 500 amps. The negative numbers on the Y-axis below zero representcurrent in amps that will be generated by the KERS system under brakingwith a scale of zero to −300 amps of regeneration. It should be notedthat the charge and discharge current profile reflects the conditions ofthe racetrack, such as its layout, length, elevation, topography, aswell as the desired performance of the vehicle such as lap time, desiredspeed and acceleration. These and other conditions, upon which a currentprofile in accordance with an exemplary embodiment described herein isgenerated, may be collected experimentally or from other commerciallyavailable sources.

Both plots have the same peak discharge currents of approximately 450amps during acceleration events. The top plot shows the KERS systemcurrent profile if a KERS system limit of 5 C is imposed on the motorcontroller, for example by an ECU. For an exemplary electricalaccumulator comprised of a 30 Ah battery pack, a KERS system currentlimit of 5 C results in a 150 amp KERS system charge limit (30 Ah×5C=150 Amps), which can be seen in this plot as the KERS braking eventsare truncated at the −150 mark on the graph. It may be desirable for aperson practicing the invention to impose such KERS system limits inorder to avoid overcharging the electrical accumulator, to reduce thestress on the mechanical or hydraulic KERS system componentstransmitting energy from the front wheel, or for other reasons.

The bottom plot shows the KERS system current profile if a KERS systemlimit of 7 C is imposed on the motor controller. For an exemplaryelectrical accumulator comprised of a 30 Ah battery pack, a KERS systemcurrent limit of 7 C results in a 210 amp KERS system charge limit (30Ah×7 C=210 Amps). It may be desirable for a person practicing theinvention to impose such KERS system limits in order to avoidovercharging the electrical accumulator, to reduce the stress on themechanical or hydraulic KERS system components transmitting energy fromthe front wheel, or for other reasons. Note that very little truncationis seen on the bottom plot indicating that if the rider continues toduplicate similar braking events such as during a race, a KERS systemcharge limit of 7 C or 7.5 C would be appropriate and this is themaximum level of regeneration for this exemplary rider on this exemplarytrack that could be expected by a person practicing the invention.

FIG. 12B is a plot resulting from a race simulation test performed on acandidate electrical accumulator, in this case a lithium-ion polymerbattery cell having a capacity of 30 Ah, a maximum voltage of 4.2 VDC, anominal voltage of 3.7 VDC, and a minimum cell voltage of 2.7 VDC.Lithium-ion polymer cells are known to be capable of very high dischargecurrents, but may catch on fire or explode if care is not taken duringcharging. Since a KERS system in accordance to exemplary embodiments maydeliver significant charging energy to the electrical accumulator duringthe operation of a KERS system equipped motorcycle, it is desirable tounderstand how a candidate electrical accumulator such as a battery cellwill respond when subjected to a continuous barrage of charge anddischarge cycles, often in rapid succession.

Accordingly, the inventors have designed numerous tests to simulate theconditions that a candidate battery would be subjected to on amotorcycle equipped with a KERS system in accordance with exemplaryembodiments described herein. In an exemplary test, the data collectedfrom an exemplary race track, such as the data from FIG. 12A herein, isused to construct a protocol of charge and discharge cycles and theirhold times that a candidate battery cell must be able to endure. Theresults of this test inform a person of critical areas such as whether abattery pack including one or more of the candidate battery cells willoperate safely without fire, whether the battery cell will complete acertain race distance while outputting a certain power level, how longthe charge in the battery cell can be expected to last based on certaindischarge and KERS system regeneration levels, as well as additionalinformation such as battery cell temperatures.

In the exemplary test of FIG. 12B, a candidate battery cell was fullycharged to 4.2 VDC, subjected to alternating cycles of discharge at 13.5C (405 Amps) with a hold time of 5.9 seconds, followed by a KERS systemcharge at 5 C (150 Amps) with a hold time of 6.75 seconds. Thesealternating discharge/charge cycles were continued until the voltage ofthe battery cell reached the minimum voltage of 2.7 VDC. The batterycell voltage is seen in FIG. 12B as solid lines, and the alternatingdischarge/charge cycles are seen as dashed lines representing amps. Fromthis plot, it can be appreciated that when exposed to a series ofnon-stop discharge/charge cycles at high current levels, the candidatebattery cell provided the requested energy for a period of between 15˜16minutes before the cell voltage spiked down to the minimum voltage of2.7 VDC. Without the benefit of the KERS system regeneration provided,the battery cell would quickly become discharged, reaching the minimumvoltage of 2.7 VDC in much less time than the 15˜16 minutes observed inthe exemplary test of FIG. 12B.

FIG. 13 is another plot depicting an advantage that a KERS system inaccordance with exemplary embodiments provides for a motorcycle relativeto an identical motorcycle without a KERS system. Using a battery packwith a power to weight performance level of 100 Wh/Kg (average forlithium-ion battery packs currently available in the art), a personpracticing the invention may easily determine from FIG. 13 the batterypack capacity that will be required for a desired horsepower level inorder to complete a fixed length event such as an electrical motorcyclerace. From this plot, it can easily be appreciated that for a givenhorsepower level, the KERS system according to exemplary embodimentsallows the use of a much lower capacity battery pack providing anassociated weight reduction over an identical, non KERS system,motorcycle of approximately 100 lbs weight savings.

FIG. 14 is another plot depicting an advantage that the KERS system inaccordance with exemplary embodiments may provide for a motorcyclerelative to an identical motorcycle without a KERS system. Electricmotor controllers typically specify maximum and minimum voltage rangeswithin which they can deliver maximum power from a connected electricmotor. Below the minimum max power voltage (320 VDC in this exemplaryembodiment), the electric motor controller and electric motor maycontinue to operate and make power, but at a reduced level. Using anexemplary battery pack providing a voltage range of 420 VDC fullycharged, it can easily be appreciated that while the motorcycles withand without a KERS system start at the same initial voltage, themotorcycle with a KERS system (“the KERS motorcycle”) experiences avoltage rise during each braking event, whereas the motorcycle without aKERS system (“the non-KERS motorcycle”) experiences flat voltage duringeach braking event. Accordingly, the non-KERS motorcycle quickly reachesthe minimum voltage level and cannot complete an exemplary race of 20miles, while the KERS motorcycle completes the race at maximum power.Although references are made to race tracks and race performance, it canbe appreciated that significant application and advantages may also beobtained to non-racing motorcycles in a wide variety of operatingconditions.

FIG. 15 is another plot depicting an advantage that the KERS system inaccordance with exemplary embodiments may provide for a motorcyclerelative to an identical motorcycle without a KERS system. In this plot,an exemplary race is broken down to a single lap to facilitate analysisof battery pack capacity savings. An exemplary embodiment is depicted bythe asterisk symbol “*” on the plot. In this embodiment, a mechanicalKERS system has been designed with the capability of transferring 450lbs of braking force from the front wheel (X-axis), and when combinedwith a KERS Current Limit of approximately 5 C, results in the need of abattery pack capacity of 3 Ah per lap (Y-axis). Compared with anidentical non-KERS motorcycle requiring 4.1 Ah per lap, a savings of 1.1Ah per lap, or a 13.2 Ah total battery pack reduction for an exemplary12-lap electric motorcycle race is realized. The associated weightsavings experienced by the KERS reduced battery pack in this analysis isbetween 80˜130 lbs based on the range of commercially availablelithium-ion batteries in the art.

FIG. 16 is another plot depicting an advantage that the KERS system inaccordance with exemplary embodiments may provide for a motorcyclerelative to an identical motorcycle without a KERS system. The top plotshows that for an exemplary desired power level of 194 horsepower shownby the asterisk “*” (approx 486 amps on the X-axis), a non-KERSmotorcycle would require a battery pack capacity of 4.1 Ah per lap(y-axis), whereas the KERS motorcycle requires a capacity of only 3 Ahper lap. Referring then to the bottom plot, if the non-KERS motorcyclewere fitted with a battery pack having a capacity of only 3 Ah per lap(i.e. 73% on the Y-axis of the full capacity 4.1 Ah pack), a horsepowerlimit would need to be imposed to limit the maximum power to 35%(X-axis) of the available power (from 194 horsepower down to 68horsepower) in order for a non-KERS motorcycle to travel the samedistance as the KERS motorcycle, such as 12 laps of an electricmotorcycle race. Therefore, if a non-KERS motorcycle and a KERSmotorcycle both feature the same 3 Ah per lap battery pack and the sameelectric motor, in order to complete the same 12-lap race, the non-KERSmotorcycle must be limited to just 68 horsepower, while the KERSmotorcycle can produce 194 horsepower for the entire race distance.

In accordance with the above described embodiments of the front wheelmechanical KERS system for a motorcycle, the transfer of the power fromthe front wheel to the electrical accumulator may be accomplishedthrough a rigid drive system, at least partially internal to the vehicleframe that enables a full range of steering, that maintains vehicleaesthetics, and prevents rider injury from exposed front wheel driveparts. As discussed previously, the mechanical KERS system may extendalong one or both sides of the front wheel. In a preferred embodiment,the mechanical KERS system extends along both sides of the front wheeland is symmetrically aligned along the axis of steering tocounterbalance and thus minimize the torque reactions from the rotationof the moving parts.

In an alternative embodiment, the KERS system described above may beused without a front wheel sprag clutch. Using the same mechanical KERSsystem described above but without a front wheel sprag clutch, the frontwheel would in effect be driven by the motor. In so doing, the vehiclemay be made to be a two-wheel drive or all wheel-drive vehicle, or evensolely a front-wheel drive. In an exemplary embodiment a front-wheeldrive or a two-wheel/all-wheel drive vehicle may still be able toregenerate energy in the electrical accumulator during deceleration asdescribe above. In an exemplary embodiment of a front wheel drivevehicle the rear wheel may be left to free wheel without beingoperatively engaged to the motor shaft.

Another exemplary embodiment may include a hydraulic energy recoverysystem (“hydraulic KERS system”) fully or partially replacing the abovedescribed mechanical KERS system. A hydraulic KERS system in accordancewith an exemplary embodiment may also be connected to the front wheeland may be engaged to transfer power from the front wheel to theelectrical accumulator by way of the electric motor. A hydraulic KERSsystem may include at least one hydraulic pump to pump fluid and onehydraulic pump to receive the pumped fluid known as a hydraulic motor.In one embodiment, two gerotors are used, one installed on the frontwheel and one connected to the motor shaft. In one embodiment, thegerotor engaged with the front wheel can be used to generate pressure.The pressure is then transferred to a hydraulic motor connected to themotor shaft using a conduit or fluid passageway such as tubing. Thehydraulic motor may also comprise a gerotor. The pressure transfer maybe accomplished using a liquid such as hydraulic fluid or oil astypically used in gerotors. The hydraulic motor connected to the motorshaft converts the pressure energy transferred from the first gerotorinto a load applied to the motor shaft by using the pressure energy torotate the motor shaft. Upon application of this load to the motorshaft, the motor can then generate electricity upon receipt of a commandfrom the motor controller as explained above with respect to themechanical KERS system embodiments. The commands and sensors controllingthe motor, operation and engagement of the hydraulic KERS system may besimilar to those described above in conjunction with the mechanical KERSsystem. Accordingly, engagement of the hydraulic KERS system may bemanual, automatic, or a combination of both.

An advantage derived from using a hydraulic KERS system as describedherein is the ability to collect energy from the front wheel without theneed of the mechanical gears and shafts described in conjunction withthe mechanical KERS system. Accordingly, a hydraulic KERS system may beeasier to implement with different vehicle designs than a mechanicalKERS system. For example a hydraulic KERS system may be easily employedin motorcycles that do not have a front fork such as, for example,motorcycles that use a hub steering or swingarm style front suspension.

An exemplary embodiment of the hydraulic KERS system is shown in FIG.17A. This figure shows a motorcycle 300 equipped with a first hydraulicpump 310 operatively connected to a front wheel, a hydraulic motor 320operatively connected to the electric motor, a valve 330, a reservoir340, a conduit or tubing 350.

An exploded view of an exemplary embodiment of the first hydraulic pump310 is shown in FIG. 17( b). The first hydraulic pump 310 may include agerotor assembly 311 having a housing 312, made for example of aluminum,a housing cover 313, a gerotor 314, a shaft 315, and tubing 350. Thegerotor 314 may be made of any known material, in one exemplaryembodiment the gerotor 314 is made of powdered metal. A steel plate mayalso be inserted between the powdered metal gerotor and the aluminumhousing to prevent galling.

As the front wheel spins, it operatively engages and turns front wheelshaft 315 that is connected to gerotor 314. As front wheel shaft 315turns, it rotates gerotor 314 thereby causing fluid from tubing 350 tobe suctioned in from the reservoir 340 and pressured toward hydraulicmotor 320. Front wheel shaft 315 and gerotor housing cover 313 arerepresented as a solid front wheel shaft and solid cover, however, incertain embodiments it may be desirable for the axle of the front wheel106 to pass through the center of the gerotor pump assembly. In suchembodiments, front wheel shaft 315 may be hollow, and the front wheelaxle may pass through the center of the front wheel shaft and exitthrough the center of the gerotor housing cover and be thereto rotatablysealed by the use of one or more o-rings or other suitable sealingdevices arranged to seal against a rotating shaft as are known by thoseskilled in the art of hydraulic systems.

An exploded view of an exemplary embodiment of the hydraulic pump/motor320 is shown in FIG. 17( c). The hydraulic motor 320 may include agerotor assembly 321 having a housing 322, made for example of aluminum,a housing cover 323, a gerotor 324, an motor shaft 325, and tubing 350.The gerotor 324 may be made of any known material, in one exemplaryembodiment the gerotor 324 is made of powdered metal. A steel plate mayalso be inserted between the powdered metal gerotor and the aluminumhousing to prevent galling.

As the pressurized fluid from the hydraulic pump 310 is received byhydraulic motor 320 from tubing 350, it causes the gerotor 324 to turn.As the gerotor 324 turns it applies a load on the output shaft 325 thatis operatively connected to the electric motor. When the load is appliedit can be turned into electrical energy by the electric motor. In ahydraulic KERS system, the controls for the electric motor to generatepower to recharge the electrical accumulator may be the same as thosedescribed above with respect to the mechanical KERS system.

As the pressurized fluid causes the gerotor 324 to turn, it leaves thehydraulic motor 320 by way of tubing 350 and returns to reservoir 340.As shown in FIG. 17( a), the hydraulic KERS system may be engaged anddisengaged using, for example, a valve 330. In an exemplary embodiment,valve 330 may be a 2-position valve such as a solenoid operated or acable operated valve. The 2-position valve may be engaged or disengaged.When the 2-position valve is engaged the tubing 350 allows the fluid totravel from reservoir 340, to first hydraulic pump 310, to hydraulicmotor 320 and back to reservoir 340. When the 2-position valve 330 isdisengaged, the tubing 350 is effectively split into two allowing fluidto circulate only between reservoir 340 and first hydraulic pump 310,while effectively isolating hydraulic motor 320.

An exemplary diagram of the operation of the hydraulic KERS system isfurther illustrated in FIG. 17( d). As explained above, this diagramshows the flow of fluid from the reservoir to the first hydraulic pumpoperatively connected to the front wheel, to the hydraulic pump/motoroperatively connected to the electric motor and finally back to thereservoir.

Like the mechanical KERS system described previously, the hydraulic KERSsystem may be operated manually, automatically, or a combination ofmanual and automatic operation. Similar to the mechanical KERS system, amanual operation may include a switch or lever for example on thehandlebars for the rider to operate. For example, valve 330 may be acable operated valve, where the cable is directly connected to the leveron the handlebar. Valve 330 may be operated, for example to switchbetween the A position and the B position indicated in FIG. 17( a).

The hydraulic KERS system provides many of the same advantages describedabove with respect to the mechanical KERS system. Importantly, thehydraulic KERS system in accordance with an exemplary embodiment isconnected to the front wheel and thus is able to generate substantialenergy during operation of a motorcycle. This in turn allows for the useof lighter weight electrical accumulators and extended vehicle range. Ahydraulic KERS system may also be easily designed to accommodate for thetelescoping action of the front fork by the implementation of flexibletubing. Finally, like the mechanical KERS system described previously,the hydraulic KERS system may be designed to power the front wheel byconfiguring the front hydraulic pump and the hydraulic motor to bothfunction as hydraulic pump/motors. The structure of a hydraulicpump/motor is similar to that of a the hydraulic pump 310 and hydraulicmotor 320 discussed above with the exception that they are able tofunction in both manners to receive and transfer power between them. Byusing two hydraulic pump/motors, it would be possible to transfer powerto and from the front wheel thereby allowing for KERS systemregeneration during deceleration while also achieving front wheel driveor two-wheel/all-wheel drive.

In yet another embodiment, a mechanical KERS system may be used asdescribed previously, except with the addition of a dual clutch packdifferential mounted on the motor shaft. The dual clutch pack may allowfor additional control of the engagement and disengagement of the motorshaft with the front wheel KERS system and with the rear wheel. A dualclutch pack may be used in combination with the sprag bearings on thefront wheel and jackshaft. Alternatively, the dual clutch pack may beused without the sprag bearings, thereby providing for full control ofthe engagement and disengagement of the motor shaft with the KERS systemand with the rear wheel.

An exemplary embodiment of a dual clutch pack differential is shown inFIG. 18. This figure provides a cross-sectional view of a dual clutchpack differential mounted on the motor shaft. FIG. 18 shows, an electricmotor 410 with an motor shaft 412. The motor shaft may be splined toengage with an inner clutch basket 414. The outer edge of the innerclutch basket 414 includes a collar portion 416 that may be designed toallow for the position of the inner clutch basket 414 relative to theposition of an outer pressure plate 420 and of an inner pressure plate422. The inner edge of the inner clutch basket 414 may further besimilarly provided with a collar portion 418 designed to aid thepositioning of the inner clutch basket 414 relative to the outerpressure plate 420 and inner pressure plate 422.

Opposite the inner clutch basket 414 may be an outer clutch basket 424.Outer clutch basket 424 may be connected to rear wheel sprocket 432 andmotor KERS sprocket 430, which are each engaged with chains as describedpreviously. A series of clutch friction plates 426 and clutch metaldiscs 428 may be provided between the inner clutch basket 414 and theouter clutch basket 424. Clutch friction plates 426 and clutch metaldiscs 428 may be splined to either the inner clutch basket 414 or theouter clutch basket 424.

According to this exemplary embodiment, when the mechanical KERS systemis to be engaged, the inner pressure plate 422 can be fixed in itsposition while the collar portion 416 of inner clutch basket 414 may bepressed toward the pressure plate 422 thereby pressing against theclutch friction plates 426 and clutch metal discs 428 operativelyengaged with motor KERS sprocket 430. In so doing, the mechanical KERSsystem connected to sprocket 430 is operatively engaged to the motorshaft. Alternatively, when power is to be transferred to the rear wheel,the outer pressure plate 420 is pressed against the inner clutch basket414, which is may be held fixed in its position by collar portion 416thereby pressing against the clutch friction plates 426 and clutch metaldiscs 428 operatively engaged to rear wheel sprocket 432. In so doing,power is transferred to the rear wheel by way of sprocket 432. It shouldalso be recognized that if desired, the outer pressure plate 420 may bepressed inwards against the pressure plate 422 thereby pressing againstall of the clutch friction plates 426 and clutch metal discs 428operatively engaged to both the motor KERS sprocket 430 and the rearwheel sprocket 432. This would result in the mechanical KERS system andthe rear wheel being simultaneously engaged with the motor shaft. Thismay be desired to achieve simultaneous power transfer from the electricmotor to the front and rear wheels.

FIG. 19 provides an additional exemplary embodiment in which suspensionfor the front wheel may be provided outside the front fork such as usedin a BMW Telelever®. In this exemplary embodiment, suspension 500extends between the vehicle frame 501 and bottom member 502 connected tothe steering mechanism at location 503. In this exemplary embodiment thefront fork 504 may still be a telescopic front fork as described above.Front fork 504 may also still contain additional suspension elements.The KERS system apparatus, mechanical or hydraulics, used in thisexemplary embodiment would be the same as those described above inconjunction with the other exemplary embodiments.

Exemplary embodiment shown in FIG. 19 may also be an optional designthat eases the construction of a mechanical or hydraulic KERS systemwithin the front fork. As described above, a KERS system may be formedalong the front fork or alternatively inside the front fork. A KERSsystem apparatus would be the same as described above in conjunctionwith the other exemplary embodiments with the exception of beingenclosed within the front fork as opposed to being adjacent to the frontfork. As shown in FIG. 19, because the suspension may be providedoutside the front fork, more room would be available inside the frontfork making the implementation of a KERS system within the front forkeasier because there would not be any need to share the space withsuspension elements such as springs and damping valves.

In yet another exemplary embodiment, a mechanical KERS system may alsobe implemented for use in motorcycles and other vehicles that use a hubsteering or swingarm style front suspensions. In such exemplaryembodiments (not shown) where the front swingarm remains fixed relativeto a pivoting front wheel, a universal joint may be mounted on the frontwheel to allow power transfer from the front wheel while providing for afull range of steering. The universal joint may be connected to either asprocket or other gear. In one embodiment, the sprocket is mounted onswingarm side of the universal joint and may operatively engage a chainthat extends and operatively engages to the motor shaft like the KERSdrive chain as described above. Alternatively, a universal joint on thefront wheel may be connected to a gear that can transfer power to adrive shaft similar to the KERS front shafts 170 or 180 described abovethat can extend inside of the vehicle frame extending along the frontswingarm. Inside the vehicle frame, the drive shaft may be designed todirectly engage a gear box similar to gear box 160 described above thatis also connected to a KERS drive chain operatively engaged to the motorshaft. Like the exemplary embodiments previously disclosed, two driveshafts may also be used instead of a single drive shaft. In such analternative embodiment, each drive shaft would operatively engage thefront wheel on opposite sides of the front wheel axle each using auniversal joint to allow the front wheel to pivot during steering whilestill transferring energy to the electric motor.

It will be apparent to those skilled in the art that variousmodifications and variation can be made in the present invention withoutdeparting from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

We claim:
 1. A method of regenerating energy in an electricalaccumulator comprising: collecting energy from a kinetic energy recoverysystem (“KERS”) operatively connected to a front wheel of a two-wheel orthree-wheel vehicle; transferring energy collected from the front wheelalong a steering head to an electric motor by applying a load on a motorshaft; generating electricity using the load applied on the motor shaft.2. The method of claim 1, wherein the kinetic energy from the frontwheel is mechanically transferred from the front wheel to the motorshaft.
 3. The method of claim 1, wherein the kinetic energy from thefront wheel is transferred from the front wheel to the motor shaft usinghydraulics.
 4. The method of claim 1, wherein generating electricityfurther comprises: collecting data from one or more sensors on thevehicle; determining an appropriate level of regenerative torque basedon the collected information; initiating said regenerative torque in themotor.
 5. The method of claim 4, wherein collecting data furthercomprises at least one of: measuring a state of charge of at least oneelectrical accumulator on the vehicle; measuring a speed of at least onewheel; measuring a tilt angle of the vehicle; and measuring the positionof the vehicle with respect to a destination.
 6. A method comprising:calculating an amount of charge current obtainable from a front wheelkinetic energy recovery system (“KERS”); calculating a current level andduration for a desired duty cycle for an electrical accumulator for atleast one discharge event and one energy recovery event; and testing theelectrical accumulator using the calculated current level and durationfrom each event.
 7. The method of claim 6, further comprising:generating a current profile based on the testing; and limiting chargingof the electrical accumulator by the KERS using the current profile viaa motor controller.
 8. The method of claim 7, further comprising:limiting discharging of the electrical accumulator using the currentprofile via a motor controller when approaching a minimum voltage levelof the electrical accumulator.
 9. The method of claim 7 wherein thecurrent profile reflects at least one of the following: elevation,topography, route time, desired speed, and desired acceleration.
 10. Themethod of claim 1, wherein the transferring energy step furthercomprises: applying the load on the motor shaft using a chain or gear.11. The method of claim 10, wherein the motor shaft is substantiallyrigid and comprises a light weight material.
 12. The method of claim 5,further comprising limiting the initiated regenerative torque based onthe tilt angle of the vehicle.
 13. The method of claim 1, furthercomprising: detecting a charge level of the electrical accumulator; andusing a friction braking system when the detected charge level of theelectrical accumulator is in a state of high charge.
 14. The method ofclaim 13, wherein the friction braking system and the KERSsimultaneously provide braking force to slow the vehicle.
 15. The methodof claim 13, wherein a proportion of braking force provided by thefriction braking system and the KERS is determined by a control unit.16. The method of claim 15, wherein the control unit comprises an enginecontrol unit.
 17. The method of claim 15, wherein the control unitcomprises a motor controller.
 18. The method of claim 13, wherein aproportion of braking force provided by the friction braking system andthe KERS is determined by an operator of the vehicle.
 19. The method ofclaim 1, further comprising: allowing the front wheel and a rear wheelof the vehicle to spin at different speeds to thereby create a deadzone.
 20. The method of claim 19, wherein the dead zone provides for aminimum gear ratio between the rear wheel and a motor, the dead zoneexpressed by:(r _(r) /r _(m))≧(r _(f) /r _(m))×(R _(r) /R _(f))_(max)×((1+s_(f))/(1+s _(r)))_(max) wherein the variable “R” represents wheelradius, “r” represents effective gear pitch radius, and “s” representsslip ratio, wherein the subscript “r” represents rear wheel, “f”represents front wheel, and “m” represents motor.
 21. The method ofclaim 19, wherein the dead zone provides for a minimum gear ratiobetween the front wheel and the motor, the dead zone expressed by:(r _(f) /r _(m))≦(r _(r) /r _(m))*(R _(f) /R _(r))_(min)*((1+s_(r))/(1+s _(f)))_(min) wherein the variable “R” represents wheelradius, “r” represents effective gear pitch radius, and “s” representsslip ratio, wherein the subscript “r” represents rear wheel, “f”represents front wheel, and “m” represents motor.
 22. The method ofclaim 19, wherein the dead zone allows the front and the rear wheels tofree wheel in one direction.
 23. The method of claim 19, furthercomprising: the motor engaging a rear wheel sprag bearing while a frontwheel sprag bearing is disengaged and overrunning during acceleration.24. The method of claim 19, further comprising: the motor disengaging arear wheel sprag bearing and engaging a front wheel sprag bearing duringdeceleration.
 25. The method of claim 19, further comprising:disengaging a rear clutch and engaging a front clutch during braking.26. A method comprising: collecting data from one or more sensors, thedata including a position of a vehicle relative to an intendeddestination, tilt angle, and state of charge of an electricalaccumulator; determining appropriate kinetic energy recovery system(“KERS”) control based on at least the position of the vehicle, tiltangle, and electrical accumulator state of charge, the appropriate KERScontrol allowing the vehicle to reach the intended destination; andinitiating torque commands in a motor based on the determined KERScontrol thereby controlling the motor.
 27. The method of claim 26,wherein the torque commands override at least one input received from anoperator of the vehicle.
 28. The method of claim 3, wherein hydraulicpressure is generated by a hydraulic pump driven by the front wheel. 29.The method of claim 28, wherein the hydraulic pump is a gerotor.
 30. Themethod of claim 28, wherein the hydraulic pressure is conveyed viatubing to a second hydraulic pump connected to the motor shaft.
 31. Themethod of claim 30, wherein the second hydraulic pump is configured as ahydraulic motor.
 32. The method of claim 11, further comprising:controlling engagement and disengagement of the motor shaft with theKERS and rear wheel with a dual clutch pack differential.
 33. The methodof claim 32, wherein the dual clutch pack differential is mounted on themotor shaft.